intermittent. no power, low idle

I was going to junk yard yesterday coincidentally. After 20 min on the highway then dropping ole lady off at her sis house, I turn a corner, all of a sudden at around 30 in 5th the car just loses all power. I downshifted through all gears to 1st to barely make it conveniently to an auto zone on the same block. I noticed then the rpm at idle at 500, if it dropped below it would go to 300 and jump to 1000 for about six or seven times. Engine would respond to gas pedel and rev at sit still. So. I checked all coil packs by unplugging one at a time. Every time I unplugged one it didn't make the slightest difference in sound or rev. So I figured it couldn't be that since if every coilpack was bad it obviously wouldn't run at all. Then I noticed almost a more straight through sound coming from the converter area as if something broke free or. So I assumed 02 sensor leak or header leak from running something over and not paying attention. Alas. No leak as I crawled under and felt for rushing air. I checked oil level. Put a quart in to bring it dead top line full. I started the car again. It was fine. I scratched my head and drove away. I made it three blocks and the car did it again. But this time. Tue car idleing for about 20 sec seemed to catch on and it set itself back to norm. I regained power and everything since has been dandy. Anyone share this experienced symptoms?

intermittent. no power, low idle